The present invention relates to a device for generating wave motion in a water test tank or the like by moving a wave generating board in the tank and specifically to a device of the wet back type, where water circulates at the back, as well as at the front of the wave generating board. Such devices are traditionally used to produce wave formations to scale to study the action of the waves on harbour installations, sand bars, the motions of vessels, the forces on structures, or such like.
It is well known, for example see U.S. Pat. No. 3,557,559, to generate waves in a test tank by reciprocating a planar wave board in a to and fro, linear fashion parallel to the plane of the water level in the tank. It is also well known to create surface waves in a body of liquid, see U.S. Pat. No. 4,406,162 by flapping a wave board in a tank by rocking it about a horizontal pivot point.
Devices are also known which in addition to being capable of operating in either of the fashions described above, are also capable of operating in a combined fashion, that is to say a fashion where the movement of the wave board is part linearly reciprocal and part pivotal.
In wet back type devices when the wave height is a maximum in front of the wave generating board, it is a minimum behind the wave generating board. This causes water jets to be propelled through the gaps between the wave boards. These are known to cause undesirable disturbances in the waves.